1. Observance of the obligations referred to in Article 18(2) by subcontractors is ensured through appropriate action by the competent national authorities acting within the scope of their responsibility and remit.

2. In the procurement documents, the contracting authority may ask or may be required by a Member State to ask the tenderer to indicate in its tender any share of the contract it may intend to subcontract to third parties and any proposed subcontractors.

3. Member States may provide that at the request of the subcontractor and where the nature of the contract so allows, the contracting authority shall transfer due payments directly to the subcontractor for services, supplies or works provided to the economic operator to whom the public contract has been awarded (the main contractor). Such measures may include appropriate mechanisms permitting the main contractor to object to undue payments. The arrangements concerning that mode of payment shall be set out in the procurement documents.

4. Paragraphs 1 to 3 shall be without prejudice to the question of the main contractor’s liability.